Method for relining a branch conduit of a main conduit

ABSTRACT

The invention relates to a method for relining an underground branch conduit (10) of an underground main conduit (11) by a relining pipe (14) in the form of a radially stiff double-walled pipe with a corrugated outer wall (14A) and a smooth elastic inner wall (14B) being inserted by use of a traction rope (22), a draw shoe (20) and a pressure plate (25). A stop element (27) is provided on the traction rope (22), which can be pressed against the draw shoe by the motion of the traction rope in relation to the draw shoe.

The invention relates to a method for relining an underground branchconduit of an underground main conduit by a relining pipe being insertedinto the branch conduit and brought to tight engagement with the mainconduit.

Damaged or leaky pipelines can be relined in several ways but especiallypreferred are methods in which a relining pipe is inserted into thedamaged pipeline. The advantage of these methods is that extensiveexcavation and digging work can be avoided since the work mainly can beperformed from existing manholes. Prolonged interruptions in industrialareas as well as traffic diversions can thereby be avoided.

One method for relining pipeline systems with branch conduits comprisesrelining first of the main conduit and then of the branch conduit atight connection then being accomplished between the main conduit andthe branch conduit.

According to U.S. Pat. No. 4,029,428 relining of the branch conduit isaccomplished after relining of the main conduit, by the relining pipebeing pushed into the branch conduit from the upstream end thereof, i.e.the end opposite to the end connected to the main conduit. Then a tightconnection is formed between the relined main conduit and the relinedbranch conduit by introduction of polyurethane foam via the branchconduit, which is allowed to set in the junction area, and a connectionpassage is cut between the main conduit and the branch conduit from thebranch conduit at the junction site.

According to GB-A-2,326,158 relining of the branch conduit isaccomplished by a relining pipe being pushed into the branch conduitfrom the upstream end thereof a sealing element a being provided at thefront end of the relining pipe. The sealing element is pushed into themain conduit then to be drawn back into the branch conduit to a sealingposition at the junction site thereof. A sealant is then injectedbetween the branch conduit and its relining pipe.

However, these methods involve a practical drawback when the relining ofthe branch conduit takes place from the upstream end thereof by pushingthe relining pipe into the branch conduit since the upstream end seldomhas a man-hole but often has a covering on a vertical riser. From hereit is almost impossible to install relining pipes without destructivemeasures. Therefore, relining from the upstream end can be difficult toaccomplish and furthermore complicates sealing of the junction betweenthe main conduit and branch conduits. Also, high the axial flexibilityof the relining pipeis requiredwhen the inner diameter of the mainconduit is small;, it may be as small as 170 mm.

Other methods for relining branch conduits, e g according toGB-A-2,213,230, involve the introduction of a relining pipe with adeformed cross section. This requires processing of the pipe in order todeform it before as well as after the insertion thereof so that the pipecan regain its circular cross sectional shape after insertion. Accordingto additional methods a stocking-shaped element is pulled into the pipe,which is hardened after a circular cross sectional shape having beenimparted to it, a process which is complicated. Both these methods arevery expensive.

According to EP-A1-0,487,179 and GB-A-2,041,147 a flexible hose having aflange is introduced into a branch conduit via a main conduit by meansof a rope or the like, the flange being brought into sealing engagementagainst the inside of the main conduit and the inside of a relining pipein the main conduit, respectively.

A flexible hose is a cylindrical body which is essentially unable totake up radial compressive forces as well as axial bending forces. Thus,it is not suitable to install a hose in for example a sewer, which isthe main application of the present application, considering the forceswhich must be taken up by the hose, such as earth loads and groundwaterpressure. This is particulary true when the conduit in which therelining pipe has been inserted is defect and cracked or has evenruptured into several pieces due to external forces.

EP-A1-0,213,674 discloses a radially stiff (circumferentially stiff)plastic pipe with a corrugated outer wall and an elastomeric smoothinner wall which is flexible enough to be passed through a verticalshaft to an underground pipeline which extends substantiallyhorizontally. This pipe has the radial stiffness which is desired forrenewal of an underground pipeline, and it is at the same time flexibleenough to be bent in a substantially right angle without being buckledor broken in pieces.

The purpose of the invention is to provide a method of the kindmentioned above, which allows the introduction of a radially stiff butflexible relining pipe into the branch conduit without the relining pipebeing subject to excessive tensile strain and it is at the same timegauranteed that the flange is pressed with necessary force against theinside of the relining pipe in the main conduit.

In order to achieve this purpose the method according to the inventionhas obtained the characterizing features of claim 1.

In order to explain the invention in more detail an illustrativeembodiment thereof will be described below reference being made to theaccompanying drawings in which

FIG. 1 is a fragmentary perspective view of a conventional pipelinesystem with a main conduit and a branch conduit connected to it,

FIG. 2 is an axial cross sectional view of a main conduit with a branchconduit connected to it shown in plan view,

FIG. 3 is a fragmentary plan view of relining pipes for a main conduitand a branch conduit, and

FIG. 4 is an axial cross sectional view of the relining pipe for abranch conduit with a draw shoe, a traction rope and a pressure plate.

FIG. 1 shows a branch conduit (service pipe) 10 for a house. The conduitis located in the ground outside the house and one end thereof isconnected to an underground main conduit 11.

Assuming that the pipeline system, including the main conduit 11 and oneor more branch conduits 10, need to be renewed, the connections of thebranch conduits with the main conduit are first mapped, which can bemade in a known manner, for example by the introduction of a markerthrough the branch conduit up to the place where it opens into the mainconduit. The marker can be detected by a robot which is introduced intothe main conduit or by scanning the main conduit by means of a cameraintroduced into it. The distances to the openings of the branch conduitsin the main conduit are then determined from a place on the main conduitwhere a manhole is available or a shaft has been provided. Thismeasurement is combined with an angle measurement for determination ofthe angular position of the branch conduit opening in the main conduit.Then, a relining pipe 12 is introduced into the main conduit 11 by meansof known techniques. In the present case this relining pipe is assumedto consist of a radially stiff (circumferentially stiff) double-walledpipe of weldable plastic with a smooth inner wall and a corrugated outerwall, the inner wall consisting of an elastomer so that the reliningpipe can flex relatively easily. As mentioned above, such a pipe isdescribed in EP-A1-0,213,674. On the basis of the earlier performedmeasurements holes are then made in the relining pipe 12 by means of arobot which is introduced into the main conduit at the openings of thebranch conduits.

In order to renew the branch conduit 10 according to the method of theinvention, a drawing element is introduced from the upstream end of thebranch conduit in the house and further into the main conduit andthrough the same up to the manhole or the shaft. This drawing elementcan consist of a pipe eel which is pushed through the pipelines, or arope which is flushed or blown through the pipelines. The pipe eel orrope drawn through the pipelines can be used to pull in a traction wirerope. These operations are easily performed through an aperture of avertical riser without destructive measures.

A radially stiff (circumferentially stiff) relining pipe 14 of the samenature as the relining pipe 12 but with a diameter adapted to the branchconduit and a length adapted to the length of the branch conduit to berelined is provided at one end thereof with a connecting piece 15 ofthermoplastic, FIG. 2 and 3. The connecting piece is pushed over the endof the relining pipe and is welded to the relining pipe at 16. Theconnecting piece has a flange 17 which is curved according to the insideof the relining pipe 12. A sealant is applied on this flange at 18, andthe flange has electric heating wires embedded therein. The flange isfurthermore provided with an elastic sealing ring 19. The heating wirescan be of the type SWJ (Swedish joint). The relining pipe is at itsother end provided with a draw shoe 20 which is attached to the reliningpipe by means of bolts 21 and has a semi-spherical dome-like portion 20'protruding from the end of the pipe, as shown in FIG. 4.

The traction wire rope, designated 22 in FIG. 4, inserted into the mainand branch conduits, is guided through an aperture 23 in the draw shoe20 and can pass freely through this aperture. The traction wire rope ispulled through the relining pipe 14 to the other end thereof where itvia a spring 24 is secured to a pressure plate 25 which is kept centeredon the flange 17 by means of a border 26. The border has a height whichis smaller than the thickness of the flange. A stop element 27 isattched to the rope, which cannot pass through the hole 23 but can beapplied against the draw shoe when the spring 24 is stretched as thetraction wire rope is being pulled.

When pulling the wire rope 22, the introduction of the relining pipe 14takes place initiallt by the relining pipe being pushed forward underpressure against the flange 17 via the pressure plate 25 in order not tosubject the relining pipe to excessive tensile stress and accompanyingelongation. When the relining pipe has to pass from the main conduitinto the branch conduit at a substantially right angle, an increasedresistance to movement of the relining pipe will be exerted withaccompanying increase of the pulling force of the traction wire rope.Then difficulties may arise in pushing the relining pipe from the mainconduit into the branch conduit. As the tractive force increases, thespring 24 will be stretched and the stop element 27 will be pressedagainst the draw shoe 20 at the hole 23 as a supplement to thecompressive force via the pressure plate, movement into the branchconduit thus being facilitated.

In a further embodiment of the invention the spring is excluded and thefunction thereof between the traction rope and the draw shoe arises bythe inner pipe being axially compressed under the influence of thepulling force in the traction rope when the resistance to theintroduction of the inner tube into the branch conduit is increased.

When the relining pipe is in place in the branch conduit with the flange17 applied against the inside of the relining pipe 12, the flange has tobe attached to it.

Electric connection wires (not shown) connected to the heating wiresaccompany the relining pipe 14 and have such a length that they areaccessible from the manhole or the shaft. While keeping the flange 17pressed against the inside of the relining pipe 12 (the stop element mayhave been removed previously so that the pulling force in the tractionwire rope acts directly on the pressure plate in order to enhance thepressure on the flange), current is allowed to flow through the heatingwires 18 so that a layer of the flange melts and attaches to therelining pipe 12. With the flange 17 welded to the relining pipe 12 andwith the sealing ring 19 therebetween a tight connection is achievedbetween the relining pipe 14 of the branch conduit and the relining pipe12 of the main conduit. The relining pipe is tightly connected to thebranch conduit 10 in a known way at the upstream end of the reliningpipe. No difficulties arise here since this end of the branch conduit iseasily accessible.

Then injection of a setting sealant is made between the relining pipesand the relinded conduits. When the sealant has set, the pressure plate25 is removed by withdrawing it by means of an attached rope which wasdrawn into the pipe 12 at the same time as the pipe 14 and is accessiblefrom the manhole or the shaft.

It should be mentioned that even if the main conduit is not providedwith a relining pipe, relining of the branch conduit can take place inthe way mentioned above. In this case, the tight connection between themain conduit and the relining pipe must take place by injection ofsealant since weldings against pipes of cement or concrete cannot beaccomplished.

I claim:
 1. Method for relining an underground branch conduit (10) of anunderground main conduit (11), the method comprising the steps of:introducing into the branch conduit via the main conduit a relining pipe(14) with a substantially circular cross section adapted to the branchconduit, tightly connecting to the main conduit on the inside thereof aflange (17) at one end of the relining pipe, using as a relining pipe aradially stiff double-walled pipe with a corrugated outer wall (14A) anda smooth elastic inner wall (14B), attaching a draw shoe (20) to theother end of the relining pipe (14), introducing a traction rope (22)through the branch conduit (10) into and through the main conduit (11)as well as through the draw shoe and the relining pipe, securing saidrope to a pressure plate (25) in said other end of the relining pipe,and providing a stop element (27) on the traction rope (22), which canbe applied against the draw shoe by the motion of the traction rope inrelation to the draw shoe.
 2. Method as claimed in claim 1, furthercomprising the step of connecting a spring (24) between the pressureplate (25) and the draw shoe (20).
 3. Method as claimed in claim 1,further comprising the step of applying a sealant on the flange (17) fortight connection of the relining pipe (14) to the main conduit (11). 4.Method as claimed in claim 1, further comprising the step of welding theflange (17) to the inside of the main conduit (11) by fusing the plasticmaterial thereof by electric heating by means of resistance wires (18)in or on the flange (17).
 5. Method as claimed in claim 1, furthercomprising the step of applying a gasket (19) between the flange (17)and the inside of the main conduit (11).